I see that S&W has started putting a big Performance Center logo on the side of the magazine well.

I bought mine (M&P 15 AR 5.56) in 2008 but it doesn't have any such logo. In fact, from the outside, you can't see it's a performance center gun, other than maybe the stainless barrel. You have to look at the end label on the box it came in to see it's a PC gun.

Bud's guns has a PC for sale and I guess they're using an old stock photo cause it doesn't have the logo either.

When did they start putting that on the rifle?